In various applications, it can be useful to delay the transmission of an electrical signal. For example, such delayed transmissions can be used to synchronize signals for various circuits. This synchronization allows integrated circuits to work properly. The transmission of an electrical signal can be delayed in various ways.
A delay unit (DU) is an electrical element that can delay the transmission of an electrical signal. A DU can receive a signal and then, after a time delay, generate a delayed signal. The delayed signal generated by the DU can have the same properties as the signal received by the DU, except that the delayed signal can have the time delay added by the DU. A particular DU can have a time delay that is a fixed amount of time, however different DUs can have different time delays. A coarse DU (CDU) can have a relatively longer time delay than a fine DU (FDU). As examples, a CDU may have a time delay of 200 picoseconds and a FDU may have a time delay of 12.5 picoseconds. However, CDUs and FDUs of various time delays are available.
A delay line (DL) is an electrical element that can delay the transmission of an electrical signal by using one or more DUs connected together in a line of DUs. A DL can receive a signal and then, after a time delay, generate a delayed signal. A particular DL can have time delays for varied amounts of time. The time delay of a DL can be varied by electrically shifting one or more DUs into or out of the line of DUs used by the DL. A DL can use none of the DUs in a line of DUs, to generate a signal with a time delay of zero. A coarse DL (CDL) with a line of CDUs can have relatively longer time delays than a fine DL (FDL) with a line of FDUs. As an example, a CDL may use a line of ninety-six CDUs, each with a time delay of 200 picoseconds, for time delays in increments of 200 picoseconds. As another example, a FDL may use a line of sixteen FDUs, each with a time delay of 12.5 picoseconds, for time delays in increments of 12.5 picoseconds.
A DL system is an electrical system that can delay the transmission of an electrical signal by using one or more DLs connected together. A DL system can include one or more CDLs and/or one or more FDLs and/or one or more other electrical elements. A particular DL system can have time delays for varied amounts of time. The time delay of a DL system can be varied by electrically shifting one or more DUs into or out of one or more DLs of the DL system.
Throughout this document, electrically shifting a CDU into or out of a CDL in a DL system is referred to as “remote coarse-shifting” and electrically shifting an FDU into or out of an FDL in a DL system is referred to as “fine-shifting.” Remote coarse-shifting can cause issues in a DL and/or a DL system. A remote coarse-shift can consume a significant amount of power for an integrated circuit. For example, a remote coarse-shift can draw instantaneous current on the order of one milli-amp. The power consumption from a remote coarse-shift can also adversely affect a power supply for the DL and/or the DL system, e.g. this can cause jitter in the delayed electrical signal generated by the DL and/or the DL system. Such jitter can disturb the synchronization of an integrated circuit, causing it to work improperly.